It's a dangerous subject, but it only takes a slight change in wording to turn a take-all-the-marbles conflict into a positive example of you offering them an opportunity. See,

"Give me remote or I walk."

Versus,

"I found this great role at this other company, and the work they do satisfies me on a deep personal level. However, it's not remote, and if you let me stay remote, my present position would be way better. What do you feel would be right?"

One is an ultimatum/threat, and the other is simply expressing facts/position as part of a negotiation (it also reserves your right to act however you choose, and does not immediately put the relationship in jeopardy). The former is not advisable, ever.

I recommend everyone read Getting to Yes.

I second the Getting to Yes recommendation. It's the best book I've found on negotiating that is actually applicable in the real world.

Except the second one is only useful if you actually do have another offer, so the two are not equivalent.

What you should actually do is politely request that you be allowed to work remotely, as you "realized that you are not looking forward to spending a significant chunk of your day commuting, and have realized that remote work is much better for your mental health". This is still a polite request, but fairly clear that you'll probably start looking for another job if they deny.

Exactly. Being assertive and firmly negotiating doesn’t mean you have to be a jerk. Just the opposite, actually: if you’re being a jerk, you’re probably not not negotiating well.

Bingo. The above example is great as well -- "I'd like to stay here, but being remote matters more to me. How can we solve this amicably?"

Only if you're truly willing to lose your job, in which case you hold all the cards, and if not you gotta go back to the office.

I think the point is if you respect each other you will find a solution without stooping to brinkmanship.